Not Applicable.
Not Applicable.
This application is the divisional application of patent application Ser. No. 10/091,410 and the material contained in the parent application is hereby incorporated herein by this specific reference. This invention relates to the design of a pin clutch to allow for coupling of a rotational shaft to an output mechanism in a synchronous fashion. Specifically, this is related to impacting or operations requiring intermittent or semi-intermittent coupling of an input mechanism or shaft to an output mechanism or shaft. Devices of this nature include fastening tools, throwing mechanisms and other devices in which input energy is built up during a portion of a cycle followed by the coupling and release of that energy to an output mechanism. This invention relates generally to portable electromechanical devices. Such devices are typically less than 30 pounds and are completely suitable for an entirely portable operation.
Devices often are required to couple an input shaft to an output mechanism in a fashion which allows for a high transfer of energy over a limited output period. The nature of direct coupling allows for a quick, efficient and robust energy or motion transfer. Such applications can include throwing devices such as pitching mechanisms, impacting mechanisms such as nailers, staplers, riveters and cutting operations which require a swift cutting action to avoid damage to substrates.
The most common type clutches used for these types of devices are based on frictional or complicated electromechanical means such as a pin shifting by means of a solenoid.
All of the currently available devices suffer from a number of disadvantages that include:
1. Complex design. Frictional engagements often have many close tolerance parts that require complex assembly. Additionally, since the transfer is by frictional means, the normal force required between the plates is often very large. Mechanical clutches with pins are often shifted by solenoids or other electrical means adding to the complexity of the design. Additionally, for high-speed engagement, timing elements must be included to enable repeatable action.
2. High Output Inertia to Size Ratio. Frictional clutches require large surfaces to enable a long lasting design. These larger surface requirements increase the output inertia and size of the clutch for a given amount of energy transfer.
3. Wear. Frictional clutches have wear items in the form of the friction plates. These friction plates by design have a limited life. Direct acting clutches often have the engagement parts running at large relative speeds which contributes to wear. Pin clutches in which the pin rides on a stationary activation plate wear excessively at high speeds since the relative speed of the pin to the actuation plate is high.
4. Complex operation. Currently available pin clutches which operate on solenoids to move a pin in and out of engagement or a camming means to move a pin in and out of engagement suffer from a complicated design. The timing must be accurately controlled leading to increased cost. Additionally, for rapidly rotating clutching mechanisms, the timing becomes quite critical.
5. Difficult to control. Often these types of clutches will require sensing means to determine the position of the various elements in order to engage and disengage the input shaft from the output mechanism.
In accordance with the present invention, a pin clutch is described which allows for synchronous clutching of energy or motion between an input shaft and an output shaft or mechanism. It is especially suitable for intermittent operations in which the typical cycle begins with the input shaft starting from a rest point, movement for a certain period, engaging the output mechanism, disengaging the output mechanism and then the input coming back to a resting condition. For example, the input shaft is accelerated from a known state and, within a prescribed amount of rotation, allows for transfer of energy to an output device for a certain period of rotation. This invention permits a completely mechanical setup to control a time period for building up energy on the input side of the pin clutch and then a positive transfer of motion or energy to the output device. The clutch disengagement is purely by mechanical means either by spring return or a positive acting lobe on a cam surface thus disengaging the inputs and outputs. Often in intermittent mechanisms, this could be followed up with either another acceleration period to store more energy on the input side or a brake and possible stopping of the input shaft. The cycle is repeated in a synchronous fashion as controlled by the selection of the various inputs associated with the design of this clutch.
Accordingly, in addition to the objects and advantages of the synchronous pin clutch as described above, several objects and advantages of the present invention are:
1. To provide a clutching element which engages and disengages in a synchronous fashion.
2. To provide a clutching element which permits robust engagement and disengagement of an input and output in a repeatable fashion.
3. To provide a clutching mechanism which does not have frictional elements that are subject to wear when coupling high inertia loads.
4. To provide a clutching mechanism which has a very high power transfer to size ratio.
5. To provide a clutching mechanisms which has compliance during engagement positions thus reducing impact stresses.
6. To provide a clutching mechanism which is especially suitable for intermittent operations in which the input shaft is cycled and comes back to a resting state.
7. To provide a clutching mechanism which is very inexpensive and simple.
Further objects and advantages will become more apparent from a consideration of the ensuing description and drawings.